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BIO120 Lecture 3: Darwin's Evidence for Evolution + Chapters 2-4…

BIO120 Lecture 3: Darwin's Evidence for Evolution + Chapters 2-4

Geology

Found fossils of mammals that no longer existed

Discovery of transitional fossils later on justifies this

Steno's principle of superposition considered strata from all around the world to compile geological record (not all layers are present in one area) --> gave relative ages of rocks --> radiometric dating later used to give actual age of rocks

Outcome:

Earth is old --> long time for evolution / gradual changes

Intermediate forms provide evidence of common ancestors linking features of living organisms

Fossils in younger strata must resemble modern species more; remodeling old into new

Homology: patterns of similarity among organisms that reflect common ancestry

Vestigial organs: feature that was ancestors' adaptation but has either lost its usefulness or been co-opted for new uses (NOT functionless, just no longer performs what it was originally adapted for)

Flightless ostriches/emus/kiwis

Blind cavefish live in caves

Human appendix was important to leaf-eating ancestors; discovered to provide refuge for gut bacteria when infection removes them from digestive system

Goosebumps are indicative of tiny muscles attached to base of body hair that contract in response to cold or adrenaline

Atavisms: sporadically expressed remnants of ancestral features via re-expression of formerly functional genes that have been silenced by natural selection

Whales contain genetic information for making legs

Human embryos have tail that almost always disappears

Tissue lining from mouse's jaw into chicken --> molecules from mouse reawaken dormant development program for making teeth in chickens

Dead genes/pseudogenes: once useful but no longer intact or expressed

GLO makes vitamin C from glucose in other organisms (primates missing pathway due to inactivation possibly caused by ample vitamin C in diet)

Many olfactory receptor genes have been silenced in humans --> recognize less airborne molecules (each gene produces different protein/olfactory receptor); proof that dolphins evolved from land mammals as they contain OR genes

Monotremes (platypus) are only mammals that have active egg-laying gene